Apparatus and method for resistance welding tubular parts

A resistance projection welding apparatus for resistance welding a wire to a tube, the wire having a pair of axially spaced apart projections located on a welding surface, said apparatus comprising:

• a weld gun having a first and a second electrode being displaceable relative to each other, said first electrode having a first arcuate contact face engaging the wire between the pair of axially spaced apart projections at a surface opposite to the welding surface, said second electrode having a second arcuate contact face engaging the tube at a given surface, said first and said second electrode being movable to apply a force to the wire and the tube to force them together for resistance welding said wire to said tube through said pair of projections;
• wherein said second arcuate contact face engages the tube over an arcuate angle and an axial length sufficiently large enough to distribute the force applied to the tube to limit deformation of said tube thereby minimizing displacement between said first and said second electrode;
• a weld controller coupled to the weld gun for applying a welding power to said first and said second electrode to effect welding of the wire to the tube;
• a displacement sensor coupled to the weld gun for generating a displacement sensor signal responsive to displacement between said first and said second electrode;
• and
• a test computer cooperating with the displacement sensor and the weld controller, said test computer processes the displacement sensor signal to cooperate with said weld controller to terminate the welding power when displacement between said first and said second electrode during welding falls within a predetermined displacement range indicative of properly resistance welding the wire to the tube.

A resistance projection welding apparatus for resistance welding a head-rest tube to a seat-frame tube, the seat-frame tube having an annular cross section with a concave portion defining two parallel ridges, said apparatus comprising:

• a weld gun having a first and a second electrode being displaceable relative to each other, said first electrode having a first arcuate contact face engaging the seat-frame tube at a surface opposite to the concave portion, said second electrode having a second arcuate contact face engaging the head-rest tube at a given surface, said first and said second electrode being movable to apply a force to said head-rest tube and said seat-frame tube to force them together for resistance welding said head-rest tube across the two parallel ridges of said seat-frame tube;
• wherein said first and said second arcuate contact face respectively engage said seat-frame tube and said head-rest tube an arcuate angle and an axial length sufficiently large enough to distribute the force applied to each of the tubes to limit deformation of said tubes thereby minimizing displacement between said first and said second electrode;
• a weld controller coupled to the weld gun for applying a welding power to said first and said second electrode;
• a displacement sensor coupled to the weld gun for generating a displacement sensor signal responsive to displacement between said first and said second electrode;
• and
• a test computer cooperating with the displacement sensor and the weld controller, said test computer processes the displacement sensor signal to cooperate with said weld controller to terminate the welding power when displacement between said first and said second electrode during welding falls within a predetermined range indicative of properly resistance welding the head-rest tube to the seat-frame tube.

A resistance projection welding apparatus for resistance welding tubular parts together, said apparatus comprising:

• a stationary electrode having a first arcuate contact face engaging a first tubular part;
• a weld gun having a welding electrode being displaceable relative to the stationary electrode, said welding electrode having a second arcuate contact face engaging a second tubular part, said welding electrode being movable to apply a force to the second tubular part and the first tubular part to resistance weld them together;
• wherein said first and said second arcuate contact face respectively engage said first and said second tubular part over an arcuate angle and an axial length sufficiently large enough to distribute the force applied to said first and said second tubular part to limit deformation of said first and said second tubular part thereby minimizing displacement between said stationary and said welding electrode;
• a weld controller coupled to the weld gun and the stationary electrode for applying a welding power to the stationary and the welding electrode to effect welding of the first and the second tubular part;
• a displacement sensor coupled to the weld gun for generating a displacement sensor signal responsive to displacement between the stationary and the welding electrode;
• and
• a test computer cooperating with the displacement sensor and the weld controller, said test computer processes the displacement sensor signal to cooperate with said weld controller to terminate the welding power when displacement between the stationary and the welding electrode falls within a predetermined displacement range indicative of properly resistance welding the first and the second tubular part together.

A method for resistance projection welding a first and a second tubular part together, said method comprising the steps of:

• providing a weld gun having a first and a second electrode being displaceable relative to each other, said first and said second electrode having a first and a second arcuate contact face, said first and said second arcuate contact face respectively engaging the first and the second tubular part at a surface opposite to a predetermined welding surface on said first and said second tubular part;
• moving said first and said second electrode to apply a force to said first and said second tubular part to force them together for resistance welding them at the predetermined welding surface;
• distributing the force applied to said first and said second tubular part to limit deformation to minimize displacement between said first and said second electrode by utilizing sufficiently large enough first and second arcuate contact faces;
• applying a welding power to said first and said second electrode by utilizing a weld controller;
• generating a displacement signal responsive to displacement between said first and said second electrode during welding using a displacement sensor coupled to the weld gun;
• processing the displacement signal by using a test computer in cooperation with the displacement sensor;
• and
• terminating the welding power when displacement between said first and said second electrode falls within a predetermined displacement range indicative of properly resistance welding said first and said second tubular part together by using the test computer in cooperation with the weld controller.